The Congo plague outbreak - how did it happen?

The current outbreak of pneumonic plague around an open pit diamond mine at Zobia in the Ituri district, Orientale province of the northern Congo, is a highly disturbing development in world health. It illustrates just how fragile is our relationship with the biophysical environment, and how easy it is to upset the delicate balance that exists between human populations and zoonotic infections permanently maintained in remote natural reservoirs.

Ironically, it is almost 100 years to the day when Australia experienced its one and only outbreak of pneumonic plague, when this most dreaded of bacterial infections broke out in the small Queensland town of Maryborough. That was in 1905, when Maryborough was Queensland’s largest port. A wharf worker had the misfortune to encounter plague, probably from fleas off rats aboard a visiting ship from Asia. One of his children was later found to be sleeping on sacks taken from a recent ship which came from Hong Kong.

The resulting infection quickly transformed into the pneumonic form, and within a few days five of his children and a neighbour had died of plague, as well as two nurses who had looked after the children in the Maryborough Hospital. Fortunately, there were no more cases but the ensuing fear, panic and hysteria totally consumed the town, and a huge crowd gathered to witness the family’s house being burnt to the ground by Health officials.

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Contrary to popular opinion, plague has not disappeared from our world but remains more geographically widespread today than at any time in its previous history .Unlike bubonic plague which is spread to human populations by the bite of a flea, pneumonic plague is communicated directly from person to person via the mechanism of airborne droplets projected from the lungs during speaking, sneezing or coughing. The disease is characterised by an overwhelming pneumonia marked by cough, bloody sputum, high fever and chills. Untreated, death inevitably follows within a few days.

Indeed, pneumonic plague is among the deadliest of diseases and if antibacterial therapy is not initiated within 24 hours, death quickly follows. While a largely uncommon form of plague, last century the world saw a number of epidemics of the pneumonic form. This included one in Manchuria in 1910-11 which killed more than 60,000 people, and smaller epidemics in California between 1919 and 1925. Fortunately, the Maryborough outbreak, which only killed a handful of people, remains Australia’s only major encounter with this form of plague.

Plague is in many ways a fascinating disease. Primarily, a disease of small ground-living animals, which only very rarely affects humans, the disease is permanently maintained in the micro-climate of the animal’s warrens beautifully adapting itself to their lifestyle and behaviour. Some animals die from plague, others get low level infections, some become immune. Very rarely an epizootic (an epidemic among animals) rolls over the community, and it is probably at this moment that local human populations are at their most vulnerable.

The Congo epidemic, which is reported to involve hundreds of cases and so far about 61 deaths (by now, probably many more), illustrates other truths about plague. First, plague remains endemic in many parts of the world, including the Congo, which usually produces at least 1,000 cases a year.

Second, if you interfere with or modify the physical environment in the vicinity of a natural reservoir of plague (as seems to have been the case in the Congo) you run the risk of disturbing that delicate balance that exists between micro-organisms, animal and human populations, and place humans at risk. Mining and the struggle for control of rich natural resources, would have played a part here but much more important would have been the years of war and violence that have characterised much of the Congo since the late 1990s.

Third, once it became evident that an epidemic was raging, panic prevailed, and many of the 7,000 miners employed at the mine adopted the time honoured solution to plague and fled back to their villages or into the forest, probably infecting hundreds of others in the process. This has undoubtedly made the task for local authorities and the WHO in containing the epidemic and instituting a program of isolation, quarantine, treatment and contact tracing, very difficult indeed.

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What possible implications does such an epidemic hold for countries like Australia, given that plague if recognised is easily treatable and that we are geographically distant from plague’s heartlands? Well, from one perspective it demonstrates just how fragile is the equilibrium that exists between human populations and the biophysical environment. At another, in an increasingly interconnected and hyper-mobile world, where one can be in the Congo one day, but walking around central Sydney 18 hours later, no one should feel safe.

Finally, no one has ever conclusively established that plague did not establish permanent reservoirs among Australia’s wildlife as happened in California and other parts of the world in the first decade of last century. Is it possible that plague smoulders away as a natural infection of small animals in Australia?